U.S. patent number 5,897,588 [Application Number 08/818,621] was granted by the patent office on 1999-04-27 for coronary stent and method of fabricating same.
Invention is credited to Michael D. Crocker, Cheryl C. Hull.
United States Patent |
5,897,588 |
Hull , et al. |
April 27, 1999 |
Coronary stent and method of fabricating same
Abstract
An expandable intraluminal stent having a tubular shaped member
having first and second ends defining an axial passageway
therethrough. The tubular shaped member has a multiplicity of slots
helically formed thereabout that are preferably provided in rows
wherein the slots of each row are arranged in an end to end
fashion. The tubular shaped member is initially disposable in a
radially collapsed configuration such that the device may be passed
into the lumen of a blood vessel, and subsequently expand to an
operative configuration wherein it will frictionally engage the
surrounding blood vessel wall to hold the device in fixed position
within the blood vessel lumen. In an alternative embodiment, the
stent is designed to accommodate a bifurcated vessel having a
collateral vessel extending therefrom.
Inventors: |
Hull; Cheryl C. (Anaheim,
CA), Crocker; Michael D. (Anaheim, CA) |
Family
ID: |
25225980 |
Appl.
No.: |
08/818,621 |
Filed: |
March 14, 1997 |
Current U.S.
Class: |
623/1.15 |
Current CPC
Class: |
A61F
2/91 (20130101); A61F 2/915 (20130101); A61F
2002/9155 (20130101); A61F 2/88 (20130101); A61F
2/856 (20130101); A61F 2250/006 (20130101) |
Current International
Class: |
A61F
2/06 (20060101); A61F 002/06 () |
Field of
Search: |
;623/1,11,12
;606/194,195,198 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Brittingham; Debra S.
Attorney, Agent or Firm: Stetina Brunda Garred &
Brucker
Claims
What is claimed is:
1. An expandable intraluminal stent comprising:
a) a tubular shaped member having first and second ends defining an
axial passageway therethrough, said tubular shaped member having a
multiplicity of slots helically formed thereabout wherein each slot
of said multiplicity of slots is formed to have a first elongate
segment, a second intermediate elongate segment, and a third
elongate segment, said second elongate segment being disposed said
intermediate said first and third segments, said slots being
provided in rows wherein the slots of each respective row are
arranged in an end to end fashion; and
b) wherein said tubular shaped member is initially disposed in a
first radially collapsed configuration such that said tubular
member may be passed into the lumen of a blood vessel, and
subsequently expanded to a second operative configuration wherein
said tubular member will frictionally engage the surrounding blood
vessel wall to hold said tubular member in fixed position within
said blood vessel lumen.
2. The expandable intraluminal stent of claim 1 wherein said
multiplicity of slots are so helically disposed about said tubular
structure that the first and second ends of said structure assume a
serpentine configuration.
3. The expandable intraluminal stent of claim 2 wherein said stent
further includes a multiplicity of openings radially formed about a
segment of said tubular shaped member, said openings being so
radially positioned about said tubular shaped member such that a
series of radial passageways are formed thereabout.
4. The expandable intraluminal stent of claim 1 wherein said stent
is formed of a shaped memory material which assumes said collapsed
configuration when at room temperature and which transitions to
said operative configuration when warmed to body temperature.
5. The expandable intraluminal stent of claim 1 wherein said stent
is formed of resilient, self-expanding material which is biased to
said operative configuration such that, when unconstrained, said
stent will resiliently self-expand to said operative
configuration.
6. The expandable intraluminal stent of claim 1 wherein said stent
is formed of a plastically deformable material which is initially
of said radially compact configuration, but which is subsequently
deformable to said operative configuration by the application of
pressure against said stent.
7. The expandable interluminal stent of claim 1 wherein said stent
is constructed from a unitary piece of non-welded material.
8. The expandable interluminal stent of claim 1 wherein said stent
is positionable upon a balloon catheter assembly such that said
stent may be positioned at a desired site in the lumen of said
blood vessel, said stent being designed to transition from said
first collapsed configuration to said second operative
configuration upon expansion of said balloon.
9. An expandable interluminal stent comprising:
a) a tubular shape member having first and second ends defining an
axially passageway therethrough, said tubular shape member having a
multiplicity of slots helically formed thereabout wherein each slot
of multiplicity of slots is formed to have a first elongate
segment, second elongate segment, and third elongate segment, said
second elongate segment being disposed intermediate said first and
third segments, said first and third segments extending outwardly
from said second segment at an angle between 160 degrees and 165
degrees, said first and third segments so extending from said
second segment that said first and third segments extend in
generally parallel relation to one another, said slots being
provided in rows wherein the slots of each respective row are
arranged in an end to end fashion; and
b) wherein said tubular shape member is initially disposed in a
first radially collapsed configuration such that said tubular
member may be passed into the lumen of a blood vessel, and
subsequently expanded to a second operative configuration wherein
said tubular member will frictionally engage the surrounding blood
vessel wall to hold the device in a fixed position within said
blood vessel lumen.
Description
FIELD OF THE INVENTION
The present invention relates generally to medical devices, and
more particularly, to expandable intraluminal stents for treating
narrowing of coronary or peripheral vessels.
BACKGROUND OF THE INVENTION
Cardiovascular disease, including atherosclerosis, is a leading
cause of death in the United States. In response thereto, the
medical community has developed a number of methods for treating
coronary heart disease, some of which are specifically designed to
treat the complications resulting from atherosclerosis and other
forms of coronary arterial narrowing.
The most significant and well-known development in treating
atherosclerosis, as well as other forms of coronary narrowing, is
percutaneous transluminal coronary angioplasty, more commonly known
and hereinafter referred to simply as "angioplasty". The objective
in angioplasty is to enlarge the lumen of the affected coronary
artery by imparting a radially expansive force, typically
accomplished by inflating a balloon, within the narrowed lumen of
the coronary artery.
While the affected artery can be effectively enlarged via
angioplasty, however, in some instances the vessel restenosis
chronically, or closes down acutely, negating the positive effect
of the angioplasty procedure. In such cases, such restenosis has
frequently necessitated repeat angioplasty procedures or open heart
surgery. While such restenosis does not occur in the majority of
patients, it does occur with enough frequency that such
complications comprise a significant percentage of the overall
failures of the angioplasty procedure.
To lessen the risk of restenosis, various devices have been
proposed for mechanically keeping the affected vessel open after
completion of the angioplasty procedure. Such mechanical
endoprosthetic devices, which are generally referred to as stents,
are typically inserted into the vessel, positioned across the
narrowed portion of the vessel, and then extended to keep the
passageway clear. Effectively, the stent overcomes the natural
tendency of the vessel walls of some patients to close back down,
thereby maintaining a more normal flow of blood through that vessel
than would otherwise be possible if the stent were not in
place.
Various types of stents have been proposed and can typically be
classed into one of two categories. In the first class, the stents
comprise various tubular metallic cylinders expanded by balloon
dilatation when positioned across the region or portion of vessel
to be widened. In the second class, the stents are formed of a heat
expandable material, such as nitinol or elgiloy, that are formed to
assume a radially expanded state when deployed at the afflicted
area within the lumen of the vessel. In this regard, such stents
are typically delivered to the affected area on a catheter capable
of receiving heated fluids, such as heated saline, such that once
properly positioned, the heated fluid is passed through the
catheter, thus causing the stent to expand.
Regardless of the class, significant difficulties have been
encountered with all prior art stents. Each has had its percentage
of thrombosis, restenosis and tissue in-growth, as well as varying
degrees of difficulty in deployment. Another difficulty with at
least some prior art stents is that they do not readily conform to
the vessel shape and/or do not accommodate bifurcated blood flow
caused by vessels having collateral vessels extending therefrom.
Importantly, virtually all prior art stents suffer from the
drawback of being structurally incompetent to withstand the stress
and strain when the axially expansive, dilatory force is imparted
thereto. This latter deficiency is especially problematic insofar
as the incapability of such stents to withstand the stress of an
axially expansive force may cause the stent to structurally
deteriorate and axially constrict over time or, alternatively,
migrate from the section of lumen where the stent was deployed.
As such, because of these and other complications, there has
resulted a low level of acceptance of such stents within the
medical community, and to date, such stents within the medical
community have not been accepted as a practical method for treating
chronic restenosis.
Thus, there has been a long felt need for a stent which is
effective to maintain a vessel open, which may be easily delivered
to the affected area, easily expanded to the desired size, easily
conform to the afflicted vessel, capable of treating curved vessels
with collateral vessels extending therefrom, as well as withstand
the stress and strain when an axially expansive force is imparted
thereto.
SUMMARY OF THE INVENTION
The present invention substantially reduces the complications and
overcomes the limitations of the prior art devices. In this
respect, the present invention provides for expandable intraluminal
stents characterized by stronger construction than prior art
stents. In a first embodiment, the stent comprises a tubular shaped
member having first and second ends that define an axial passageway
therethrough. The tubular shaped member has a multiplicity of
selectively shaped slots helically formed thereabout that are
preferably provided in rows wherein the slots of each row are
arranged in an end to end fashion. In an alternative embodiment,
the stent is further provided with a plurality of openings axially
formed about a portion of the stent that cooperate to define a
series of radial passageways. Such radial passageways provide for
the flow of fluid through the stent in a bifurcated manner. In both
embodiments, the tubular shaped member is initially disposable in a
radially collapsed configuration such that the device may be passed
into the lumen of a blood vessel, and subsequently expanded to an
operative configuration where it will frictionally engage the
surrounding vessel wall to hold the device in fixed position within
the blood vessel lumen.
The present invention further comprises methods of forming the
aforementioned stents. In a first preferred method, the stents are
formed by laser cutting or etching, the latter preferably by
electronic discharge etching, the multiplicity of slots and
openings upon a tubular member. Alternatively, the stents are
formed from a rolled sheet of flattened material having such slots
and openings formed thereon. With respect to the latter method, the
stent according to a first preferred embodiment is formed from a
sheet of material configured as a parallelogram extending
diagonally along a longitudinal axis. The stent according to the
second preferred embodiment of the present invention, in contrast,
is fabricated from a sheet having a generally chevron-like
shape.
The stents in accordance with the present invention may be deployed
through conventional methods including deployment via a balloon
catheter whereby the stent is positioned upon an inflatable balloon
while the stent is maintained in its radially collapsed
configuration and thereafter radially expanded, via inflation of
the balloon, such that the stent radially engages in a wall of an
anatomical passageway. Alternatively, the stents may be deployed by
advancing the same through the lumen of a conventional catheter
such that the stent, once axially advanced through the lumen of the
catheter at the distal-most end thereof, assumes the expanded
configuration and thus remains axially seated within a portion of
an anatomical passageway.
BRIEF DESCRIPTION OF THE DRAWINGS
These, as well as other features of the present invention, will
become more apparent upon reference to the drawings wherein:
FIG. 1 depicts a perspective view of an endovascular stent
according to a first preferred embodiment of the present
invention;
FIG. 2 is a perspective view of a tubular structure utilized to
fabricate the stent depicted in FIG. 1;
FIG. 3 is a side view of the stent of FIG. 1 wherein said stent is
in an unrolled, flattened configuration;
FIG. 4 is a perspective view of an endovascular stent constructed
according to a second preferred embodiment;
FIG. 5 is a side view of the stent of FIG. 4 wherein said stent is
in an unrolled, flattened configuration; and
FIG. 6 is a cross-sectional view of a bifurcating vessel having the
stent depicted in FIG. 1 and the stent depicted in FIG. 4
intraluminally disposed therewithin.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The detailed description set forth below in connection with the
appended drawings is intended merely as a description of the
presently preferred embodiments of the invention, and is not
intended to represent the only form in which the present invention
may be constructed or utilized. The description sets forth the
functions and sequence of steps for construction and implementation
of the invention in connection with the illustrated embodiments. It
is to be understood, however, that the same or equivalent functions
and sequences may be accomplished by different embodiments that are
also intended to be encompassed within the spirit and scope of the
invention.
Referring now to FIG. 1, there is perspectively illustrated a stent
device 10 constructed in accordance with a first preferred
embodiment of the present invention. As is well-known in the art,
and as will be discussed in more detail below, the stent 10 may be
utilized to reinforce or dilate numerous types of anatomical
passageways, including blood vessels, urogenital passageways and
bioducts. In relation to cardiovascular applications, the stent 10
is typically inserted into a blood vessel to dilate areas of the
vessel which have become occluded by atherosclerotic plaque or
constricted by an adjacent tumor.
As shown, the stent 10 comprises an elongate tubular shaped member
12 having a first end 14 and second end 16 that define an axial
pathway therethrough, as indicated by the letter A therethrough.
Helically formed about tubular shaped member 12 are a multiplicity
of uniformly shaped slots 18. The slots 18 are preferably formed
about tubular shaped member 12 in rows extending in parallel
relation to one another, whereby the slots 18 in each such row are
oriented in an end to end fashion.
In a preferred embodiment, each slot of said multiplicity of slots
is generally formed to have first, second and third elongate
segments, more clearly seen as 18a, 18b and 18c, respectively, of
FIG. 3. As shown, second segment 18b is disposed intermediate first
and third segments 18a, 18c with first and third segments 18a, 18c
extending in opposed directions therefrom such that first and third
segments 18a, 18c are maintained in generally parallel relation to
one another. Preferably, segments 18a and 18c are formed to extend
from second segment 18b at an angle 26, which preferably ranges
from 160.degree. to 165.degree.. As will be appreciated by those
skilled in the art, the lengths of segments 18a, 18b, 18c may be
selectively varied to provide the stent 10 a wider range of
expandability, as discussed below.
By virtue of the helical arrangement of rows of slots 18 having the
aforementioned configuration, there is thus formed a plurality of
bends 20 about the first and second ends 14, 16 of tubular shaped
structure 12. Such plurality of bends 20 are disposed in generally
parallel, convoluted relation to one another that there is thus
defined a multiplicity of serpentine convolutions 22 at each
respective end 14, 16 of the tubular shaped member 12.
As will be recognized by those skilled in the art, the tubular
shaped structure 12 will be specifically designed and configured to
assume a first radially collapsed configuration as shown, such that
the device may be passed into and selectively positioned within the
lumen of a vessel, and subsequently expanded to an operative
configuration, shown in phantom as 46, wherein such structure 12
will frictionally engage the surrounding blood vessel wall to hold
the device 10 in fixed position therewithin. In order for the
device 10 to assume both a radially collapsed configuration and
second expandable or operative configuration, such device may be
fabricated from a shape memory material, such as nitinol, which
thus enables the device to assume the collapsed configuration when
at room temperature, but which transitions to the operative
configuration when warmed to body temperature, as will occur when
such device is deployed.
Alternatively, the stent of the present invention may be formed of
resilient, self-expanding material which is biased to the operative
configuration such that when unconstrained, the device will
resiliently self-expand to the expanded, operative configuration.
Still further, the device may be fabricated from a plastically
deformable material which is initially formed to assume a radially
compact configuration, but which can subsequently be deformed to
assume the expanded, operative configuration by application of
pressure, such as a balloon catheter discussed more fully below,
against such stent. Among the biologically compatible materials
that may be utilized to construct the stents disclosed herein
include stainless steel, titanium, tantalum, nickel titanium,
elgiloy, and high strength thermoplastic polymers.
Advantageously, by providing such convolutions 22 at the respective
ends 14, 16 of the tubular shaped structure 12, the stent 10 is
provided greater structural stability and capacity to withstand
axially compressive stress within the lumen of a vessel when the
tubular shaped structure 12 is expanded to its operative
configuration than prior art stent devices. In this regard, such
convolutions 22, by virtue of their angled, convoluted
configuration, tend to cause ends 14, 16 to radially expand in a
rotational manner whereby the stress of such radial expansion about
ends 14, 16 is more strategically placed and evenly distributed
about segments 20a, as shown in FIGS. 1 and 3. The helical
arrangement of slots 18 further enables the tubular structure 12,
by virtue of its radial expansion in a rotational manner, to assume
a wider range of expandability when maintained in the operative
configuration. As will be recognized and appreciated by those
skilled in the art, by increasing the length of slot 18, the
tubular structure 12 will thus be provided with a selectively wider
range of expandability. Other prior art devices, in contrast, most
notable of which being zig-zag type stents, tend to expand in a
non-rotational manner and thus store stress in their respective
joints or apices when radially expanded. As a result, such prior
art stents are prone to structurally deteriorate over time.
Referring now to FIGS. 2 and 3, there is shown two preferred
methods of fabricating the stent 10 of the present invention.
Referring firstly to FIG. 2, there is perspectively shown tubular
shaped member 12a in an unaltered state. As is well-known to those
skilled in the art, the stent 10 depicted in FIG. 1 may be formed
from tubular shaped member 12a by forming the helically disposed
rows of slots by a laser, such as a YAG laser, or by electronic
discharge etching, as formed by an electronic discharge
machine.
FIG. 3 depicts an alternative method of fabricating the stent 10 of
the present invention by forming the same from an elongate sheet of
flattened, biologically compatible material 12b. In order for the
sheet 12b to assume a tubular configuration, the sheet 12b must
necessarily be configured as an elongate parallelogram having first
and second ends 14, 16, and thereby defining four end portions or
corners 14a, b, that extends diagonally along a longitudinal axis
LA1. In the preferred embodiment, the sheet 12b will extend
diagonally upward relative a vertical axis D at an angle 24 ranging
from 50.degree. to 55.degree., with an angle of 54.degree.47' being
most preferred. The multiplicity of slots 18 may then be formed
upon sheet 12b in rows extending in parallel relation to one
another along the longitudinal axis LA1. As discussed above, the
slots 18 will preferably be arranged in an end to end fashion and
further, will preferably be formed of angled segments 18a, 18b and
18c, as discussed above.
To cause sheet 12b to assume a tubular configuration, the opposed
ends 14, 16 of the sheet 12b are rotated in the direction shown by
the letters B and C. More specifically, bottom end portion or
corner 14a of end 14 will be rotate in the direction indicated by
the letter B such that end portion 14a mates with and is fused,
preferably by laser welding, resistance welding, soldering, brazing
or other joining methods known in the art, to complementary end
portion 14b. Concurrently with the rotation and fusion of end
portions 14a and 14b, end portion 16a of end 16 will be rotated in
the direction indicated by the letter C such that such portion
mates with and is fused to complementary portion 16b. The stent 10
of FIG. 1 will thus be formed and the same can be deployed in the
manner discussed below.
Referring now to FIG. 4, there is perspectively illustrated an
alternative embodiment 10a of the stent of the present invention.
Embodiment 10a is specifically designed and adapted for insertion
into a bifurcating vessel to thus accommodate and facilitate the
flow of blood into off-shoot directions. Similar to the first
embodiment, the second embodiment 10a comprises a corresponding
tubular shaped member 28 having first and second ends 30, 32
defining an axial passageway, depicted by the letter E,
therethrough that likewise is designed to assume a first radially
collapsed configuration as shown, and a second expanded or
operative configuration shown in phantom 48. The stent 10a
according to the second embodiment further includes a multiplicity
of helically arranged rows of uniformly shaped slots 34. However,
the multiplicity of slots 34, according to the second embodiment,
are helically arranged in different rotational directions such that
the slots emanating from first end 30 have an opposite rotational
orientation than slots emanating from second end 32.
Notwithstanding, the ends 30, 32 of the second embodiment 10a of
the stent of the present invention, as with the first embodiment,
are characterized by a plurality of bends 36 disposed in generally
parallel, convoluted relation to one another such that a
multiplicity of serpentine convolutions 38 are formed.
To provide for the flow of blood in an offshoot direction, stent
10a further includes a plurality of generally chevron-shaped
openings 40 axially disposed about a portion of a tubular-shaped
structure 28 and between the helically arranged slots emanating
from end 30 and 3nd 32. As will be recognized, such plurality of
openings 40 thus creates a series of radial passageways F that, as
will be discussed below, enable blood to flow to an off-shoot
vessel, in addition to allowing a portion of the blood to flow
axially through the tubular structure 28 as indicated by the letter
E.
The stent 10a according to the second embodiment may be formed by
etching, via electronic discharge etching, the multiplicity of
slots 34 and openings 40 about a tube of biologically compatible
material, such as 12a depicted in FIG. 2.
The stent 10a according to the second embodiment may further be
fabricated from a sheet of flattened, biologically compatible
material 28a as depicted in FIG. 5. As will be recognized, in order
for such sheet 28a to assume a tubular structure and likewise
provide for the series of radial passageways F, such sheet 28a must
be provided to have a generally chevron-like configuration that
defines a first end 30, having end portions or corners 30a, 30b,
and a second end 32, having end portions or corners 32a, 32b.
As with the first embodiment, the multiplicity of slots 34 may be
formed upon the sheet 28a in a similar manner and according to the
same structure as slots 18 formed upon first embodiment 10.
However, by virtue of the generally chevron-like shape of the sheet
28a, it will be necessary to form the multiplicity of slots such
that a first multiplicity of slots are formed upon sheet 28a in
rows extending in parallel relation to one another along
longitudinal axis LA2, and a second multiplicity of slots formed
upon sheet 28a that extend in parallel relation to one another
along longitudinal axis LA3. In a preferred embodiment,
longitudinal axis LA2 will extend in a radially opposed direction
than longitudinal axis LA3 at an angle 42 of approximately
109.degree.35'. Intermediate the rows of slots extending along
longitudinal axes LA2 and LA3 and along the central axis CA of
sheet 28a will be formed openings 40. As will be recognized, such
openings 40 shall be arranged in a generally linear manner.
In order for the stent 10a according to the second embodiment to
achieve a generally tubular configuration, it will be necessary
that the respective ends thereof 30, 32 be rotated in the
directions indicated by the letters G and H such that the
configuration as shown in FIG. 4 is achieved. Specifically, end
portion 30a of end 30 is rotated in the direction indicated by the
letter G such that end 30a mates with and is fused to the end
portion 30b of end 30. Similarly, in the portion 32a of end 32 is
rotated in the direction indicated by the letter H such that the
same mates with and is fused to end portion 32b the resultant
structure assumes a generally cylindrical structure as depicted in
FIG. 4.
The stents according to either preferred embodiment 10, 10a may be
deployed by any of several well-known techniques. In this regard,
stents 10, 10a disclosed herein may be deployed via a balloon
catheter whereby the stent is positioned upon an inflatable balloon
while the stent is maintained in its radially collapsed
configuration such that the balloon may be transluminally advanced
through an anatomical passageway to a desired treatment site, such
as one including an atherosclerotic plaque occlusion. After the
positioning of such balloon at the desired treatment site, thus
causing the stent to radially expand from its radially compressed
configuration to is operative configuration, which in turn causes
the stent 10, 10a to radially engage the inner wall of an
anatomical passageway, such as 44, 44a and 44b depicted in FIG. 6.
The balloon will then be deflated, with the balloon catheter being
removed within the anatomical passageway such that the stents 10,
10a remain operatively positioned at selected sites
therewithin.
Alternatively, should the stents 10, 10a of the present invention
be fabricated from a sheet memory or self-expanding material, such
stents may be deployed using a conventional catheter. As is known
in the art, such catheters typically have a lumen formed therein
through which stents, such as those of the present invention, may
be deployed at a desired site. In this regard, such stents may be
loaded within the lumen of the catheter and advanced therethrough
via a pusher. Once the desired site to be transluminally reinforced
is accessed by the distal end of the catheter, the stent is then
advanced through the lumen of the distal end of the catheter where
the same remains resident.
As depicted in FIG. 6, once maintained in position, stents 10 and
10a will enable blood to flow freely therethrough. In particular,
stent 10a according to the second preferred embodiment will enable
blood to flow initially from the direction indicated by the letter
I in a bifurcated manner represented by the letters K and J. Stent
10, as axially nested within a portion of anatomical passageway 44a
will thus allow blood to flow in a unidirectional manner as
indicated by the letter J.
Although the invention has been described herein with specific
reference to presently preferred embodiments thereof, it will be
appreciated by those skilled in the art that various additions,
modifications, deletions and alterations may be made to such
preferred embodiments without departing from the spirit and scope
of the invention. Accordingly, it is intended that all reasonably
foreseeable additions, modifications, deletions and alterations be
included within the scope of the invention as defined in the
following claims.
* * * * *